The present invention relates to a rubber composition for breaker cushion and a tire using the same. More specifically, the present invention relates to a rubber composition for breaker cushion whose lowering of tensile properties from heat build up is small, and a bus or truck tire using the same.
As shown in FIG. 1, a layer called breaker cushion 1 is disposed between edge part of a breaker 2 and a case (ply) 3. This breaker cushion has great influence on riding, durability and the like. Particularly, in case of using a bus or truck tire, temperature in edge part of a breaker rises remarkably, inducing heat aging to cause the edge rubber of the breaker to separate from steel cord, which means the breaker cushion part therearound inevitably receives huge heat history during running. Further, a breaker cushion rubber may be terribly hardened and broken down by external shock to the state of burst. Therefore, it is required that a breaker cushion rubber has small lowering of tensile properties from heat build up with enduring heavy load.
In this way, many performances are required for a breaker cushion rubber. Conventionally, ISAF or HAF grade carbon has been preferably mixed to a breaker cushion rubber compound from the following reason. That is, when high class carbon having a larger nitrogen adsorption specific surface area than SAF is used to improve steering stability and tensile properties, heat build up characteristic is increased. Besides, when low class carbon such as FEF is used to decrease heat build up characteristic, tensile properties are lowered.
Recently, on the other hand, prompt development of a breaker cushion rubber whose fatigue resistance is further improved compared to conventional breaker cushion rubbers is desired in accordance with development of duration and correction of tire life.
An object of the present invention is to provide a rubber composition for breaker cushion which has excellent elongation at break, strength at break, and the like after aging with maintaining steering stability, and a tire using the rubber composition for breaker cushion.
By adding 1,3-bis(citraconimidomethyl)benzene as an anti-reversion agent (xe2x80x9creversionxe2x80x9d meaning reversion of vulcanization) to a conventional breaker cushion rubber compound, property changes, particularly lowering of properties, of a breaker cushion rubber after aging are inhibited in the present invention.
That is, the present invention relates to a rubber composition for breaker cushion comprising 1,3-bis(citraconimidomethyl)benzene and 25 to 35 parts by weight of carbon black having a nitrogen adsorption specific surface area of 70 to 120 cm2/g based on 100 parts by weight of a rubber component.
In the above rubber composition for breaker cushion, the amount of 1,3-bis(citraconimidomethyl)benzene is preferably 0.05 to 1.0 part by weight.
And the present invention relates to a tire comprising the above rubber compositions for breaker cushion.